1. ¹Center for Stem Cell and Regenerative Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
2. ²Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
3. ³Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA

Correspondence: Dr DT Scadden, Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School, 185 Cambridge Street (CPZN-4265A), Boston, MA 2114, USA. E-mail: scadden.david@mgh.harvard.edu

Received 10 July 2007; Revised 5 October 2007; Accepted 8 October 2007; Published online 15 November 2007.

Abstract

The success of hematopoietic stem cell (HSC)-based therapies relies on the ability of the stem cells to both engraft and self-renew sufficiently in the bone marrow microenvironment. Previous studies identified that a number of components of bone contribute to the regulation of HSCs indicating that they participate in a stem cell 'niche'. This niche is a dynamic microenvironment that changes during development and with varying physiologic states. Components of it, such as the osteoblast, can be modulated through pharmacological treatment. Reasoning that the stem cell niche may be manipulated to augment the effectiveness of stem cell therapies, we demonstrated that daily treatment with parathyroid hormone (a clinically approved method for increasing osteoblast function) resulted in therapeutic benefit in three clinically relevant models of stem cell therapy. These results suggest that the niche may be a pharmacological target for altering stem cell function in settings of regenerative medicine.